LONDON (Reuters) – Mining giant BHP says it will fight an unprecedented English lawsuit filed by hundreds of thousands of Brazilians for multi-billion pound damages over Brazil’s worst environmental disaster.

SPG Law, a British offshoot of a U.S. litigator, represents 240,000 individuals in Brazil, 24 municipal governments, a Roman Catholic Archdiocese and members of the Krenak indigenous community and has filed three legal claims for unlimited damages over the failure of the Fundao dam in 2015. It looks set to be the largest group action heard in England.

London and Australian-listed BHP, the world’s largest mining company by market value, said it had received correspondence from the law firm but also noted it had so far committed $780 million to the Renova Foundation, an entity created by the miner and its partners to manage reparations and repairs.

“BHP will defend the action and remains committed to supporting the remediation and compensation efforts of the Renova Foundation,” a spokesman said. The collapse of the Fundao tailings dam, which stored mining waste and is owned by the Samarco joint venture between BHP and Brazilian iron ore mining giant Vale, killed 19 and spilled about 40 million cubic metres of sludge over communities, the Rio Doce and Atlantic Ocean 650 km away.

Brazil charged 22 people in 2016 with offences, including murder, over the dam’s collapse. The miners this year settled a 20 billion reais ($5.4 billion) civil claim with local authorities to establish a clean-up fund.